Bioethanol and ethanol electro-oxidation by amorphous alloys with low amount of platinum

摘要

The ethanol and bioethanol electro-oxidation on amorphous Ni_(59)Nb_(40)Pt_(0.6)Ru_(0.4), Ni_(59)Nb_(40)Pt_(0.6)Ru_(0.4) and Ni_(59)Nb_(40)Pt_(0.6)Ru_(0.2)Sn_(0.2) electro-catalysts was analyzed by electrochemical techniques such as Cyclic Voltammetry (CV) and chrono-amperometry. The different micro-particulated amorphous alloys were obtained by Mechanical Alloying (MA) during 40 h, being characterized by Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) to verify their amorphous nature. The minimum amount of platinum and the addition of co-catalysts were found to have a significant effect on catalytic response of anodic reaction. Although the tri-catalytic alloy provides smaller rate of poisoning (δ) than bi-catalytic alloys, the presence of tin does not improve the ethanol/bioethanol electro-oxidation reaction due to limit the distribution of platinum atoms by the ligand effect, avoiding alcohol adsorption. Concerning the reactivity towards bioethanol electro-oxidation, the current densities are considerably higher than ethanol one for all amorphous catalysts. The presence of small amount of acetaldehyde and formic acid in bioethanol, provides a synergic effect during electrooxidative process. On the other hand, the voltammograms for CO stripping clearly show that alloy with ruthenium possesses a better CO tolerance, decreasing the onset potential 20 and 16 mV with regard to Ni_(59)Nb_(40)Pt_(0.6)Ru_(0.4) and Ni_(59)Nb_(40)Pt_(0.6)Ru_(0.2)Sn_(0.2) alloys respectively.